From the earliest recorded uses of perfumes by the ancient Egyptians, achieving a fragrant environment has long been a goal of man. Over the centuries, man's aversion to malodor has led to the development of a variety of products for “air freshening”. These include potpourri, scented candles, aerosols and gels, each containing volatile fragrance and/or volatile odor counteractants.
Upon opening or activating an air freshener, volatile fragrances and/or volatile odor counteractants are released, masking unpleasant odors in the surrounding environment. As used in this application, the term “air freshening” means imparting a desired aroma to an environment and/or that odors in the surrounding atmosphere are masked by the volatile fragrance and/or volatile odor counteractants emitted from delivery system. Essential oils—concentrated, aromatic, volatile oils extracted from the flowers, leaves, stems, or roots that give plants their pleasing scents—are common ingredients in air freshening products. In many commercial air fresheners, essential oils are diluted with one or more carriers.
From a consumer standpoint, a need has existed, and continues to exist, for an environment that has a persistently pleasant, but not overpowering, aroma or fragrance. It has therefore been an objective of air freshener manufacturers to make products that provide a continuous, long-lasting release of a desired aroma to an environment to achieve a pleasant scent over an extended period of time. The difficulty in achieving this objective lies in the differing volatilities of the perfumery materials that make up the fragrance compositions and/or odor counteractants used in air fresheners. In order for fragrance compositions and/or odor counteractants to be effective, they must be volatilized—that is small and light enough to enter the nasal passage, be trapped by cilia and trigger one of hundreds of different olfactory receptors. However, this very volatility can make the desired aroma short-lived; once the fragrance composition and/or odor counteractant loading in an air freshener has been exhausted, the pleasantly scented environment dissipates and malodor, if present, returns.
Plastisols, mixtures of plasticizer and resin, commonly polyvinylchloride (PVC), are well-known in the art. Among the many uses of plastisols are coatings sealants, molded plastic parts (e.g., pipings, moldings).
Devices for dispensing volatile substances in the air through diffusion are well known in the art. U.S. Pat. No. 3,685,734 discloses a controlled fragrance release device comprising a vinyl plastisol resin containing an essential oil or other volatile substance that is bonded to a base supporting ply with a low vapor transmission rate and covered with a removable cover sheet that contains the volatile substance until removed or replaced.
U.S. Pat. No. 6,749,861 teaches an insect repellant composition comprising a high vapor pressure fragrance capable of repelling insects and a low vapor pressure non-fragrance insect repellant (e.g., DEET) which is soluble in the fragrance, and an absorption substrate carrier selected from the group consisting of paper, plastisol, gel, fabric, clay, wax, and plastic. More particularly, the '861 Patent discloses as preferred embodiments fragrance-containing PVC plastisol compositions for paper substrates. The insect repellant DEET is taught to be present in such embodiments at concentrations of up to about 80%. The maximum concentration of fragrance taught to be used in these embodiments is an amount which is soluble in the PVC plastisol and which does not destroy its film-forming properties (i.e., 1% to about 20%, most preferably about 13%). The present invention teaches fragrance concentrations in excess of about 90% for the purpose of air-freshening an environment.
A PVC resin fragrance delivery product has previously been commercialized and sold under the brand name Cool Foot by Medo Industries, Inc., now sold under the same name by SOPUS Products (Shell Oil). The Cool Foot product was based on plasticized PVC resin (powder or granule) with durometer readings of about 65 to about 80. It had fragrance loadings of less than about 20% and was meant to be freestanding (i.e., outside a package container or other supporting structure).
The fragrance delivery gel composition of the present invention differs from the commercially-available Cool Foot products in several respects, chief among which is the ability of the present invention to hold and deliver over four times the fragrance loadings in Cool Foot, while still maintaining the integrity of the gel delivery system. Another difference is that the fragrance delivery gel composition of the present invention surprisingly maintains the character of a low-viscosity, flowable liquid during the cooling phase (i.e., after reaching requisite processing temperatures or requisite re-melting temperatures). The gel composition of the present invention remains a low-viscosity, flowable liquid to temperatures as low as about 125° F.; below those temperatures, the present invention becomes a non-flowable gel. This unexpected attribute enables the gel composition of the present invention to be portioned into containers at temperatures considerably lower than original process temperatures or re-melting temperatures, thus greatly diminishing the loss of expensive fragrance into the environment during portioning operations. In contrast, the commercially-available “Cool Foot” product must be portioned by injection molding at temperatures in excess of 325° F. The “Cool Foot” product does not exist as a low-viscosity, flowable liquid below temperatures of 325° F. and, accordingly, cannot be portioned into open “containers” or by “open-mold casting. A further difference between the present invention and Cool Foot, is that the PVC resin in the prior art Cool Foot product was solid at room temperature. In contrast, the PVC resin used in the fragrance delivery system of the present invention is liquid at room temperature, thereby enabling it to be pumped as a liquid into a processing system.
It is known in the art that incorporating essential oils and/or fragrances into plasticized PVC in order to produce gelled fragrance compositions requires application of heat at temperatures in excess of at least about 285° F. It is also known in the art that essential oils and/or fragrances are sensitive to heat and other environmental stressors. Accordingly, there exists a long-felt but as yet unmet need for a process to manufacture plasticized PVC gelled perfumery materials that minimizes, and ideally eliminates, loss of essential oils and/or perfumery materials due to heat and other environmental stressors during the manufacturing process. The highly efficient, closed-loop manufacturing process of the present invention meets these needs. By limiting the processing time at requisite elevated temperatures, the present invention maximally maintains the concentration and integrity of the essential oils and other aroma-producing materials.
The manufacturing process of the present invention also provides economic benefits by maximizing the concentration of expensive fragrance ingredients in the post-processed finished gel composition. The thermal reversibility of the gel compositions of the present invention provides yet another economic advantage. Temperatures of at least about 285° F. are not needed to thermally reverse the gel of the present invention. Rather, lower temperatures of less than about 200° F. are sufficient to thermally reverse gel of the present invention. This attribute allows compositions of the present invention to be shipped in bulk to distribution centers for portioning and packaging. Further, during portioning and packaging, steam heat (i.e., less than about 200° F.) may be used to thermally reverse gels of the present invention. Additionally, the gel composition of the present invention can be re-melted and thereafter portioned into containers as a low-viscosity, flowable liquid to temperatures as low as about 125° F. As used in the present invention the phrase “thermally reversible” means that the aroma-releasing polymeric gel matrix of the present invention can be re-melted at temperatures from about 125° F. to less than about 200° F. and then portioned (i.e., from a drum or pail into small containers) as a low-viscosity, flowable liquid. When the portioned, low-viscosity, flowable liquid cools, it reconstitutes into a non-flowable gel. The high loadings of fragrance and/or odor-counteractants confer additional advantages including increased product life and/or reduced product physical size as well as cost reductions (in terms of packaging, transportation and logistics costs, and retail (on shelf) space). Additionally, reduced packaging produces less post consumer waste.
In addition to achieving loadings of fragrance and/or odor-counteractants up to about 96% by weight of the total composition, and the ability to deliver those loadings at a persistent rate over a prolonged period of time, the present invention meets the long-felt but unmet need for a long-acting aroma delivery matrix with exceptional clarity. As used in the present invention the phrase “long-acting” and/or “long-lasting” means gels that exude a discernable aroma in excess of 30 days, preferably in excess of 60 days and most preferably in excess of 90 days. The clear to translucent gels of the present invention can also be made in a wide range of colors through the addition of dyes and other colorants and/or opacifiers. Another aesthetic need that is met by the present invention is the ability to suspend three-dimensional decorative items, including, but not limited to, colored pigments, glitters and other small, decorative objects (e.g., figurines, artificial flowers).